// Copyright 2006 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.


// Known Issues:
//
// * Patterns are not implemented.
// * Radial gradient are not implemented. The VML version of these look very
//   different from the canvas one.
// * Clipping paths are not implemented.
// * Coordsize. The width and height attribute have higher priority than the
//   width and height style values which isn't correct.
// * Painting mode isn't implemented.
// * Canvas width/height should is using content-box by default. IE in
//   Quirks mode will draw the canvas using border-box. Either change your
//   doctype to HTML5
//   (http://www.whatwg.org/specs/web-apps/current-work/#the-doctype)
//   or use Box Sizing Behavior from WebFX
//   (http://webfx.eae.net/dhtml/boxsizing/boxsizing.html)
// * Non uniform scaling does not correctly scale strokes.
// * Optimize. There is always room for speed improvements.

// Only add this code if we do not already have a canvas implementation
if (!document.createElement('canvas').getContext) {

(function () {

    // alias some functions to make (compiled) code shorter
    var m = Math;
    var mr = m.round;
    var ms = m.sin;
    var mc = m.cos;
    var abs = m.abs;
    var sqrt = m.sqrt;

    // this is used for sub pixel precision
    var Z = 10;
    var Z2 = Z / 2;

    /**
    * This funtion is assigned to the <canvas> elements as element.getContext().
    * @this {HTMLElement}
    * @return {CanvasRenderingContext2D_}
    */
    function getContext() {
        return this.context_ ||
        (this.context_ = new CanvasRenderingContext2D_(this));
    }

    var slice = Array.prototype.slice;

    /**
    * Binds a function to an object. The returned function will always use the
    * passed in {@code obj} as {@code this}.
    *
    * Example:
    *
    *   g = bind(f, obj, a, b)
    *   g(c, d) // will do f.call(obj, a, b, c, d)
    *
    * @param {Function} f The function to bind the object to
    * @param {Object} obj The object that should act as this when the function
    *     is called
    * @param {*} var_args Rest arguments that will be used as the initial
    *     arguments when the function is called
    * @return {Function} A new function that has bound this
    */
    function bind(f, obj, var_args) {
        var a = slice.call(arguments, 2);
        return function () {
            return f.apply(obj, a.concat(slice.call(arguments)));
        };
    }

    var G_vmlCanvasManager_ = {
        init: function (opt_doc) {
            if (/MSIE/.test(navigator.userAgent) && !window.opera) {
                var doc = opt_doc || document;
                // Create a dummy element so that IE will allow canvas elements to be
                // recognized.
                doc.createElement('canvas');
                doc.attachEvent('onreadystatechange', bind(this.init_, this, doc));
            }
        },

        init_: function (doc) {
            // create xmlns
            if (!doc.namespaces['g_vml_']) {
                doc.namespaces.add('g_vml_', 'urn:schemas-microsoft-com:vml',
                           '#default#VML');

            }
            if (!doc.namespaces['g_o_']) {
                doc.namespaces.add('g_o_', 'urn:schemas-microsoft-com:office:office',
                           '#default#VML');
            }

            // Setup default CSS.  Only add one style sheet per document
            if (!doc.styleSheets['ex_canvas_']) {
                var ss = doc.createStyleSheet();
                ss.owningElement.id = 'ex_canvas_';
                ss.cssText = 'canvas{display:inline-block;overflow:hidden;' +
                // default size is 300x150 in Gecko and Opera
            'text-align:left;width:300px;height:150px}' +
            'g_vml_\\:*{behavior:url(#default#VML)}' +
            'g_o_\\:*{behavior:url(#default#VML)}';

            }

            // find all canvas elements
            var els = doc.getElementsByTagName('canvas');
            for (var i = 0; i < els.length; i++) {
                this.initElement(els[i]);
            }
        },

        /**
        * Public initializes a canvas element so that it can be used as canvas
        * element from now on. This is called automatically before the page is
        * loaded but if you are creating elements using createElement you need to
        * make sure this is called on the element.
        * @param {HTMLElement} el The canvas element to initialize.
        * @return {HTMLElement} the element that was created.
        */
        initElement: function (el) {
            if (!el.getContext) {

                el.getContext = getContext;

                // Remove fallback content. There is no way to hide text nodes so we
                // just remove all childNodes. We could hide all elements and remove
                // text nodes but who really cares about the fallback content.
                el.innerHTML = '';

                // do not use inline function because that will leak memory
                el.attachEvent('onpropertychange', onPropertyChange);
                el.attachEvent('onresize', onResize);

                var attrs = el.attributes;
                if (attrs.width && attrs.width.specified) {
                    // TODO: use runtimeStyle and coordsize
                    // el.getContext().setWidth_(attrs.width.nodeValue);
                    el.style.width = attrs.width.nodeValue + 'px';
                } else {
                    el.width = el.clientWidth;
                }
                if (attrs.height && attrs.height.specified) {
                    // TODO: use runtimeStyle and coordsize
                    // el.getContext().setHeight_(attrs.height.nodeValue);
                    el.style.height = attrs.height.nodeValue + 'px';
                } else {
                    el.height = el.clientHeight;
                }
                //el.getContext().setCoordsize_()
            }
            return el;
        }
    };

    function onPropertyChange(e) {
        var el = e.srcElement;

        switch (e.propertyName) {
            case 'width':
                el.style.width = el.attributes.width.nodeValue + 'px';
                el.getContext().clearRect();
                break;
            case 'height':
                el.style.height = el.attributes.height.nodeValue + 'px';
                el.getContext().clearRect();
                break;
        }
    }

    function onResize(e) {
        var el = e.srcElement;
        if (el.firstChild) {
            el.firstChild.style.width = el.clientWidth + 'px';
            el.firstChild.style.height = el.clientHeight + 'px';
        }
    }

    G_vmlCanvasManager_.init();

    // precompute "00" to "FF"
    var dec2hex = [];
    for (var i = 0; i < 16; i++) {
        for (var j = 0; j < 16; j++) {
            dec2hex[i * 16 + j] = i.toString(16) + j.toString(16);
        }
    }

    function createMatrixIdentity() {
        return [
      [1, 0, 0],
      [0, 1, 0],
      [0, 0, 1]
    ];
    }

    function matrixMultiply(m1, m2) {
        var result = createMatrixIdentity();

        for (var x = 0; x < 3; x++) {
            for (var y = 0; y < 3; y++) {
                var sum = 0;

                for (var z = 0; z < 3; z++) {
                    sum += m1[x][z] * m2[z][y];
                }

                result[x][y] = sum;
            }
        }
        return result;
    }

    function copyState(o1, o2) {
        o2.fillStyle = o1.fillStyle;
        o2.lineCap = o1.lineCap;
        o2.lineJoin = o1.lineJoin;
        o2.lineWidth = o1.lineWidth;
        o2.miterLimit = o1.miterLimit;
        o2.shadowBlur = o1.shadowBlur;
        o2.shadowColor = o1.shadowColor;
        o2.shadowOffsetX = o1.shadowOffsetX;
        o2.shadowOffsetY = o1.shadowOffsetY;
        o2.strokeStyle = o1.strokeStyle;
        o2.globalAlpha = o1.globalAlpha;
        o2.arcScaleX_ = o1.arcScaleX_;
        o2.arcScaleY_ = o1.arcScaleY_;
        o2.lineScale_ = o1.lineScale_;
    }

    function processStyle(styleString) {
        var str, alpha = 1;

        styleString = String(styleString);
        if (styleString.substring(0, 3) == 'rgb') {
            var start = styleString.indexOf('(', 3);
            var end = styleString.indexOf(')', start + 1);
            var guts = styleString.substring(start + 1, end).split(',');

            str = '#';
            for (var i = 0; i < 3; i++) {
                str += dec2hex[Number(guts[i])];
            }

            if (guts.length == 4 && styleString.substr(3, 1) == 'a') {
                alpha = guts[3];
            }
        } else {
            str = styleString;
        }

        return { color: str, alpha: alpha };
    }

    function processLineCap(lineCap) {
        switch (lineCap) {
            case 'butt':
                return 'flat';
            case 'round':
                return 'round';
            case 'square':
            default:
                return 'square';
        }
    }

    /**
    * This class implements CanvasRenderingContext2D interface as described by
    * the WHATWG.
    * @param {HTMLElement} surfaceElement The element that the 2D context should
    * be associated with
    */
    function CanvasRenderingContext2D_(surfaceElement) {
        this.m_ = createMatrixIdentity();

        this.mStack_ = [];
        this.aStack_ = [];
        this.currentPath_ = [];

        // Canvas context properties
        this.strokeStyle = '#000';
        this.fillStyle = '#000';

        this.lineWidth = 1;
        this.lineJoin = 'miter';
        this.lineCap = 'butt';
        this.miterLimit = Z * 1;
        this.globalAlpha = 1;
        this.canvas = surfaceElement;

        var el = surfaceElement.ownerDocument.createElement('div');
        el.style.width = surfaceElement.clientWidth + 'px';
        el.style.height = surfaceElement.clientHeight + 'px';
        el.style.overflow = 'hidden';
        el.style.position = 'absolute';
        surfaceElement.appendChild(el);

        this.element_ = el;
        this.arcScaleX_ = 1;
        this.arcScaleY_ = 1;
        this.lineScale_ = 1;
    }

    var contextPrototype = CanvasRenderingContext2D_.prototype;
    contextPrototype.clearRect = function () {
        this.element_.innerHTML = '';
    };

    contextPrototype.beginPath = function () {
        // TODO: Branch current matrix so that save/restore has no effect
        //       as per safari docs.
        this.currentPath_ = [];
    };

    contextPrototype.moveTo = function (aX, aY) {
        var p = this.getCoords_(aX, aY);
        this.currentPath_.push({ type: 'moveTo', x: p.x, y: p.y });
        this.currentX_ = p.x;
        this.currentY_ = p.y;
    };

    contextPrototype.lineTo = function (aX, aY) {
        var p = this.getCoords_(aX, aY);
        this.currentPath_.push({ type: 'lineTo', x: p.x, y: p.y });

        this.currentX_ = p.x;
        this.currentY_ = p.y;
    };

    contextPrototype.bezierCurveTo = function (aCP1x, aCP1y,
                                            aCP2x, aCP2y,
                                            aX, aY) {
        var p = this.getCoords_(aX, aY);
        var cp1 = this.getCoords_(aCP1x, aCP1y);
        var cp2 = this.getCoords_(aCP2x, aCP2y);
        bezierCurveTo(this, cp1, cp2, p);
    };

    // Helper function that takes the already fixed cordinates.
    function bezierCurveTo(self, cp1, cp2, p) {
        self.currentPath_.push({
            type: 'bezierCurveTo',
            cp1x: cp1.x,
            cp1y: cp1.y,
            cp2x: cp2.x,
            cp2y: cp2.y,
            x: p.x,
            y: p.y
        });
        self.currentX_ = p.x;
        self.currentY_ = p.y;
    }

    contextPrototype.quadraticCurveTo = function (aCPx, aCPy, aX, aY) {
        // the following is lifted almost directly from
        // http://developer.mozilla.org/en/docs/Canvas_tutorial:Drawing_shapes

        var cp = this.getCoords_(aCPx, aCPy);
        var p = this.getCoords_(aX, aY);

        var cp1 = {
            x: this.currentX_ + 2.0 / 3.0 * (cp.x - this.currentX_),
            y: this.currentY_ + 2.0 / 3.0 * (cp.y - this.currentY_)
        };
        var cp2 = {
            x: cp1.x + (p.x - this.currentX_) / 3.0,
            y: cp1.y + (p.y - this.currentY_) / 3.0
        };

        bezierCurveTo(this, cp1, cp2, p);
    };

    contextPrototype.arc = function (aX, aY, aRadius,
                                  aStartAngle, aEndAngle, aClockwise) {
        aRadius *= Z;
        var arcType = aClockwise ? 'at' : 'wa';

        var xStart = aX + mc(aStartAngle) * aRadius - Z2;
        var yStart = aY + ms(aStartAngle) * aRadius - Z2;

        var xEnd = aX + mc(aEndAngle) * aRadius - Z2;
        var yEnd = aY + ms(aEndAngle) * aRadius - Z2;

        // IE won't render arches drawn counter clockwise if xStart == xEnd.
        if (xStart == xEnd && !aClockwise) {
            xStart += 0.125; // Offset xStart by 1/80 of a pixel. Use something
            // that can be represented in binary
        }

        var p = this.getCoords_(aX, aY);
        var pStart = this.getCoords_(xStart, yStart);
        var pEnd = this.getCoords_(xEnd, yEnd);

        this.currentPath_.push({ type: arcType,
            x: p.x,
            y: p.y,
            radius: aRadius,
            xStart: pStart.x,
            yStart: pStart.y,
            xEnd: pEnd.x,
            yEnd: pEnd.y
        });

    };

    contextPrototype.rect = function (aX, aY, aWidth, aHeight) {
        this.moveTo(aX, aY);
        this.lineTo(aX + aWidth, aY);
        this.lineTo(aX + aWidth, aY + aHeight);
        this.lineTo(aX, aY + aHeight);
        this.closePath();
    };

    contextPrototype.strokeRect = function (aX, aY, aWidth, aHeight) {
        var oldPath = this.currentPath_;
        this.beginPath();

        this.moveTo(aX, aY);
        this.lineTo(aX + aWidth, aY);
        this.lineTo(aX + aWidth, aY + aHeight);
        this.lineTo(aX, aY + aHeight);
        this.closePath();
        this.stroke();

        this.currentPath_ = oldPath;
    };

    contextPrototype.fillRect = function (aX, aY, aWidth, aHeight) {
        var oldPath = this.currentPath_;
        this.beginPath();

        this.moveTo(aX, aY);
        this.lineTo(aX + aWidth, aY);
        this.lineTo(aX + aWidth, aY + aHeight);
        this.lineTo(aX, aY + aHeight);
        this.closePath();
        this.fill();

        this.currentPath_ = oldPath;
    };

    contextPrototype.createLinearGradient = function (aX0, aY0, aX1, aY1) {
        var gradient = new CanvasGradient_('gradient');
        gradient.x0_ = aX0;
        gradient.y0_ = aY0;
        gradient.x1_ = aX1;
        gradient.y1_ = aY1;
        return gradient;
    };

    contextPrototype.createRadialGradient = function (aX0, aY0, aR0,
                                                   aX1, aY1, aR1) {
        var gradient = new CanvasGradient_('gradientradial');
        gradient.x0_ = aX0;
        gradient.y0_ = aY0;
        gradient.r0_ = aR0;
        gradient.x1_ = aX1;
        gradient.y1_ = aY1;
        gradient.r1_ = aR1;
        return gradient;
    };

    contextPrototype.drawImage = function (image, var_args) {
        var dx, dy, dw, dh, sx, sy, sw, sh;

        // to find the original width we overide the width and height
        var oldRuntimeWidth = image.runtimeStyle.width;
        var oldRuntimeHeight = image.runtimeStyle.height;
        image.runtimeStyle.width = 'auto';
        image.runtimeStyle.height = 'auto';

        // get the original size
        var w = image.width;
        var h = image.height;

        // and remove overides
        image.runtimeStyle.width = oldRuntimeWidth;
        image.runtimeStyle.height = oldRuntimeHeight;

        if (arguments.length == 3) {
            dx = arguments[1];
            dy = arguments[2];
            sx = sy = 0;
            sw = dw = w;
            sh = dh = h;
        } else if (arguments.length == 5) {
            dx = arguments[1];
            dy = arguments[2];
            dw = arguments[3];
            dh = arguments[4];
            sx = sy = 0;
            sw = w;
            sh = h;
        } else if (arguments.length == 9) {
            sx = arguments[1];
            sy = arguments[2];
            sw = arguments[3];
            sh = arguments[4];
            dx = arguments[5];
            dy = arguments[6];
            dw = arguments[7];
            dh = arguments[8];
        } else {
            throw Error('Invalid number of arguments');
        }

        var d = this.getCoords_(dx, dy);

        var w2 = sw / 2;
        var h2 = sh / 2;

        var vmlStr = [];

        var W = 10;
        var H = 10;

        // For some reason that I've now forgotten, using divs didn't work
        vmlStr.push(' <g_vml_:group',
                ' coordsize="', Z * W, ',', Z * H, '"',
                ' coordorigin="0,0"',
                ' style="width:', W, 'px;height:', H, 'px;position:absolute;');

        // If filters are necessary (rotation exists), create them
        // filters are bog-slow, so only create them if abbsolutely necessary
        // The following check doesn't account for skews (which don't exist
        // in the canvas spec (yet) anyway.

        if (this.m_[0][0] != 1 || this.m_[0][1]) {
            var filter = [];

            // Note the 12/21 reversal
            filter.push('M11=', this.m_[0][0], ',',
                  'M12=', this.m_[1][0], ',',
                  'M21=', this.m_[0][1], ',',
                  'M22=', this.m_[1][1], ',',
                  'Dx=', mr(d.x / Z), ',',
                  'Dy=', mr(d.y / Z), '');

            // Bounding box calculation (need to minimize displayed area so that
            // filters don't waste time on unused pixels.
            var max = d;
            var c2 = this.getCoords_(dx + dw, dy);
            var c3 = this.getCoords_(dx, dy + dh);
            var c4 = this.getCoords_(dx + dw, dy + dh);

            max.x = m.max(max.x, c2.x, c3.x, c4.x);
            max.y = m.max(max.y, c2.y, c3.y, c4.y);

            vmlStr.push('padding:0 ', mr(max.x / Z), 'px ', mr(max.y / Z),
                  'px 0;filter:progid:DXImageTransform.Microsoft.Matrix(',
                  filter.join(''), ", sizingmethod='clip');")
        } else {
            vmlStr.push('top:', mr(d.y / Z), 'px;left:', mr(d.x / Z), 'px;');
        }

        vmlStr.push(' ">',
                '<g_vml_:image src="', image.src, '"',
                ' style="width:', Z * dw, 'px;',
                ' height:', Z * dh, 'px;"',
                ' cropleft="', sx / w, '"',
                ' croptop="', sy / h, '"',
                ' cropright="', (w - sx - sw) / w, '"',
                ' cropbottom="', (h - sy - sh) / h, '"',
                ' />',
                '</g_vml_:group>');

        this.element_.insertAdjacentHTML('BeforeEnd',
                                    vmlStr.join(''));
    };

    contextPrototype.stroke = function (aFill) {
        var lineStr = [];
        var lineOpen = false;
        var a = processStyle(aFill ? this.fillStyle : this.strokeStyle);
        var color = a.color;
        var opacity = a.alpha * this.globalAlpha;

        var W = 10;
        var H = 10;

        lineStr.push('<g_vml_:shape',
                 ' filled="', !!aFill, '"',
                 ' style="position:absolute;width:', W, 'px;height:', H, 'px;"',
                 ' coordorigin="0 0" coordsize="', Z * W, ' ', Z * H, '"',
                 ' stroked="', !aFill, '"',
                 ' path="');

        var newSeq = false;
        var min = { x: null, y: null };
        var max = { x: null, y: null };

        for (var i = 0; i < this.currentPath_.length; i++) {
            var p = this.currentPath_[i];
            var c;

            switch (p.type) {
                case 'moveTo':
                    c = p;
                    lineStr.push(' m ', mr(p.x), ',', mr(p.y));
                    break;
                case 'lineTo':
                    lineStr.push(' l ', mr(p.x), ',', mr(p.y));
                    break;
                case 'close':
                    lineStr.push(' x ');
                    p = null;
                    break;
                case 'bezierCurveTo':
                    lineStr.push(' c ',
                       mr(p.cp1x), ',', mr(p.cp1y), ',',
                       mr(p.cp2x), ',', mr(p.cp2y), ',',
                       mr(p.x), ',', mr(p.y));
                    break;
                case 'at':
                case 'wa':
                    lineStr.push(' ', p.type, ' ',
                       mr(p.x - this.arcScaleX_ * p.radius), ',',
                       mr(p.y - this.arcScaleY_ * p.radius), ' ',
                       mr(p.x + this.arcScaleX_ * p.radius), ',',
                       mr(p.y + this.arcScaleY_ * p.radius), ' ',
                       mr(p.xStart), ',', mr(p.yStart), ' ',
                       mr(p.xEnd), ',', mr(p.yEnd));
                    break;
            }


            // TODO: Following is broken for curves due to
            //       move to proper paths.

            // Figure out dimensions so we can do gradient fills
            // properly
            if (p) {
                if (min.x == null || p.x < min.x) {
                    min.x = p.x;
                }
                if (max.x == null || p.x > max.x) {
                    max.x = p.x;
                }
                if (min.y == null || p.y < min.y) {
                    min.y = p.y;
                }
                if (max.y == null || p.y > max.y) {
                    max.y = p.y;
                }
            }
        }
        lineStr.push(' ">');

        if (!aFill) {
            var lineWidth = this.lineScale_ * this.lineWidth;

            // VML cannot correctly render a line if the width is less than 1px.
            // In that case, we dilute the color to make the line look thinner.
            if (lineWidth < 1) {
                opacity *= lineWidth;
            }

            lineStr.push(
        '<g_vml_:stroke',
        ' opacity="', opacity, '"',
        ' joinstyle="', this.lineJoin, '"',
        ' miterlimit="', this.miterLimit, '"',
        ' endcap="', processLineCap(this.lineCap), '"',
        ' weight="', lineWidth, 'px"',
        ' color="', color, '" />'
      );
        } else if (typeof this.fillStyle == 'object') {
            var fillStyle = this.fillStyle;
            var angle = 0;
            var focus = { x: 0, y: 0 };

            // additional offset
            var shift = 0;
            // scale factor for offset
            var expansion = 1;

            if (fillStyle.type_ == 'gradient') {
                var x0 = fillStyle.x0_ / this.arcScaleX_;
                var y0 = fillStyle.y0_ / this.arcScaleY_;
                var x1 = fillStyle.x1_ / this.arcScaleX_;
                var y1 = fillStyle.y1_ / this.arcScaleY_;
                var p0 = this.getCoords_(x0, y0);
                var p1 = this.getCoords_(x1, y1);
                var dx = p1.x - p0.x;
                var dy = p1.y - p0.y;
                angle = Math.atan2(dx, dy) * 180 / Math.PI;

                // The angle should be a non-negative number.
                if (angle < 0) {
                    angle += 360;
                }

                // Very small angles produce an unexpected result because they are
                // converted to a scientific notation string.
                if (angle < 1e-6) {
                    angle = 0;
                }
            } else {
                var p0 = this.getCoords_(fillStyle.x0_, fillStyle.y0_);
                var width = max.x - min.x;
                var height = max.y - min.y;
                focus = {
                    x: (p0.x - min.x) / width,
                    y: (p0.y - min.y) / height
                };

                width /= this.arcScaleX_ * Z;
                height /= this.arcScaleY_ * Z;
                var dimension = m.max(width, height);
                shift = 2 * fillStyle.r0_ / dimension;
                expansion = 2 * fillStyle.r1_ / dimension - shift;
            }

            // We need to sort the color stops in ascending order by offset,
            // otherwise IE won't interpret it correctly.
            var stops = fillStyle.colors_;
            stops.sort(function (cs1, cs2) {
                return cs1.offset - cs2.offset;
            });

            var length = stops.length;
            var color1 = stops[0].color;
            var color2 = stops[length - 1].color;
            var opacity1 = stops[0].alpha * this.globalAlpha;
            var opacity2 = stops[length - 1].alpha * this.globalAlpha;

            var colors = [];
            for (var i = 0; i < length; i++) {
                var stop = stops[i];
                colors.push(stop.offset * expansion + shift + ' ' + stop.color);
            }

            // When colors attribute is used, the meanings of opacity and o:opacity2
            // are reversed.
            lineStr.push('<g_vml_:fill type="', fillStyle.type_, '"',
                   ' method="none" focus="100%"',
                   ' color="', color1, '"',
                   ' color2="', color2, '"',
                   ' colors="', colors.join(','), '"',
                   ' opacity="', opacity2, '"',
                   ' g_o_:opacity2="', opacity1, '"',
                   ' angle="', angle, '"',
                   ' focusposition="', focus.x, ',', focus.y, '" />');
        } else {
            lineStr.push('<g_vml_:fill color="', color, '" opacity="', opacity,
                   '" />');
        }

        lineStr.push('</g_vml_:shape>');

        this.element_.insertAdjacentHTML('beforeEnd', lineStr.join(''));
    };

    contextPrototype.fill = function () {
        this.stroke(true);
    }

    contextPrototype.closePath = function () {
        this.currentPath_.push({ type: 'close' });
    };

    /**
    * @private
    */
    contextPrototype.getCoords_ = function (aX, aY) {
        var m = this.m_;
        return {
            x: Z * (aX * m[0][0] + aY * m[1][0] + m[2][0]) - Z2,
            y: Z * (aX * m[0][1] + aY * m[1][1] + m[2][1]) - Z2
        }
    };

    contextPrototype.save = function () {
        var o = {};
        copyState(this, o);
        this.aStack_.push(o);
        this.mStack_.push(this.m_);
        this.m_ = matrixMultiply(createMatrixIdentity(), this.m_);
    };

    contextPrototype.restore = function () {
        copyState(this.aStack_.pop(), this);
        this.m_ = this.mStack_.pop();
    };

    function matrixIsFinite(m) {
        for (var j = 0; j < 3; j++) {
            for (var k = 0; k < 2; k++) {
                if (!isFinite(m[j][k]) || isNaN(m[j][k])) {
                    return false;
                }
            }
        }
        return true;
    }

    function setM(ctx, m, updateLineScale) {
        if (!matrixIsFinite(m)) {
            return;
        }
        ctx.m_ = m;

        if (updateLineScale) {
            // Get the line scale.
            // Determinant of this.m_ means how much the area is enlarged by the
            // transformation. So its square root can be used as a scale factor
            // for width.
            var det = m[0][0] * m[1][1] - m[0][1] * m[1][0];
            ctx.lineScale_ = sqrt(abs(det));
        }
    }

    contextPrototype.translate = function (aX, aY) {
        var m1 = [
      [1, 0, 0],
      [0, 1, 0],
      [aX, aY, 1]
    ];

        setM(this, matrixMultiply(m1, this.m_), false);
    };

    contextPrototype.rotate = function (aRot) {
        var c = mc(aRot);
        var s = ms(aRot);

        var m1 = [
      [c, s, 0],
      [-s, c, 0],
      [0, 0, 1]
    ];

        setM(this, matrixMultiply(m1, this.m_), false);
    };

    contextPrototype.scale = function (aX, aY) {
        this.arcScaleX_ *= aX;
        this.arcScaleY_ *= aY;
        var m1 = [
      [aX, 0, 0],
      [0, aY, 0],
      [0, 0, 1]
    ];

        setM(this, matrixMultiply(m1, this.m_), true);
    };

    contextPrototype.transform = function (m11, m12, m21, m22, dx, dy) {
        var m1 = [
      [m11, m12, 0],
      [m21, m22, 0],
      [dx, dy, 1]
    ];

        setM(this, matrixMultiply(m1, this.m_), true);
    };

    contextPrototype.setTransform = function (m11, m12, m21, m22, dx, dy) {
        var m = [
      [m11, m12, 0],
      [m21, m22, 0],
      [dx, dy, 1]
    ];

        setM(this, m, true);
    };

    /******** STUBS ********/
    contextPrototype.clip = function () {
        // TODO: Implement
    };

    contextPrototype.arcTo = function () {
        // TODO: Implement
    };

    contextPrototype.createPattern = function () {
        return new CanvasPattern_;
    };

    // Gradient / Pattern Stubs
    function CanvasGradient_(aType) {
        this.type_ = aType;
        this.x0_ = 0;
        this.y0_ = 0;
        this.r0_ = 0;
        this.x1_ = 0;
        this.y1_ = 0;
        this.r1_ = 0;
        this.colors_ = [];
    }

    CanvasGradient_.prototype.addColorStop = function (aOffset, aColor) {
        aColor = processStyle(aColor);
        this.colors_.push({ offset: aOffset,
            color: aColor.color,
            alpha: aColor.alpha
        });
    };

    function CanvasPattern_() { }

    // set up externs
    G_vmlCanvasManager = G_vmlCanvasManager_;
    CanvasRenderingContext2D = CanvasRenderingContext2D_;
    CanvasGradient = CanvasGradient_;
    CanvasPattern = CanvasPattern_;

})();

} // if
